Manufacturing yield and pre-mature partial operational failure are persistent problems in integrated circuit production. Built-in self-test (BIST) logic is often utilized to facilitate the testing of circuits during fabrication and/or production to identify defective circuits. Additionally, many circuit designers include redundant circuitry within the circuit in an effort to improve overall yield.
Currently, one technique for addressing various yield problems includes using the BIST logic to detect some defective but replaceable logic during the manufacturing and fabrication process and laser trimming or some other permanent modification process to bypass the defective elements. For example, with laser trimming, after the circuits are tested, a laser cuts some connections in such a way that identified defective elements are bypassed. A laser may also be used to activate available redundant logic during the permanent modification production process.
Yet another technique used to address yield problems due to pre-mature partial failures is a burn-in process that artificially ages the components being tested to eliminate those circuits in the components that experience early failures. If, after burn-in is completed, the BIST logic detects some defective but replaceable logic, permanent modification processes as previously described may be used to bypass and/or replace the defective circuitry prior to distribution.
Unfortunately, these modification techniques incur a significant cost during the fabrication and production process while providing no performance guarantee for the future. Moreover, manufacturing and production testing as previously described neither detects intermittent errors, nor repairs any such undetected errors. Additionally, operational circuit errors that develop after production are not easily repaired using production based techniques, such as laser trimming or other similar permanent modification methods.